Product code encoding is a known encoding technique that enables data to be encoded for transmission, e.g. by radio. FIGS. 1 and 2 show the principle of product encoding.
In this case a block of 90 bits is to be encoded, wherein the bits are referenced d1 to d90. The bits are organized on a table as shown in FIG. 1, the table comprising a number k1=9 of rows and a number k2=10 of columns. Product code encoding consists in applying first block encoding (referred to as row encoding) to each of the k1 rows so as to obtain additional bits referenced dli (FIG. 2) corresponding to encoding each of the k1 rows. By way of example, the bits dl1, dl2, and dl3 correspond to encoding the bits d1 to d10. As a function of the kind of block encoding scheme used, this gives rise to k1.times.n2 additional bits (in this case n2=3). These bits are placed after the bits from which they are derived, thus obtaining a table that has k1 rows and k2+n2 columns.
After this first encoding operation, a second kind of block encoding (known as column encoding) is applied to the k2+n2 columns, so as to generate n1.times.(k2+n2) additional bits. In FIG. 2, 20 additional bits (dci) are thus generated by encoding the k2 columns, and 6 more additional bits (dlci) are obtained by encoding the n2 columns. In this case the value of n1 is equal to 2. By way of example, the encoding of the bits in the first column of the table in FIG. 1 gives rise to bits dc1 and dc2.
A product code is defined on the basis of the parameters (n1, k1) and (n2, k2) of the row and column codes.
When transmitting ATM cells, it is desirable for the header to be better protected than the payload data field since the header comprises, in particular, the destination address for the cell. If the address is severely degraded on transmission, the packet as transmitted not only fails to arrive at its destination, but it is no longer possible to warn the destination that a packet intended for it has not arrived. Furthermore, when the packet reaches an unknown node, the routing system is disturbed.
A particular object of the present invention is to remedy those drawbacks.